There have been numerous advances in the easy-open can end field. Many relate to methods of forming such can ends or forming the score lines, i.e., the tear strip's tear line. Others relate to designs for the pull tab rings, their method of attachment to the can end, and the interaction between the two during opening. Other known devices relate to specific methods for forming the pull tab rings, or the shape of the score lines against which the pull tabs operate to open the can. However, all known easy-open can ends are deficient in that they require use of excessive pull tab forces to fully open the can end.
More specifically, the typical easy-open ecology can end, i.e., one where the pull tab ring remains attached to the metal can end after opening has occurred, requires an excessively deep score line in the can end metal. This is required to permit easy opening of the tear strip portion simultaneously along generally both sides of the U-shaped score line during opening. However, this has often resulted in inadvertent fractures of the can end along the score line, such as by internal forces or even by external forces directed to the can end, with attendant can contents leakage.